Method for transmitting or receiving signal in wireless communication system and apparatus therefor

ABSTRACT

According to one embodiment of the present invention, a method of receiving DCI by a UE includes receiving bundling information regarding REGs via higher layer signaling, performing blind detection for a PDCCH in a CORESET configured on a plurality of OFDM symbols, and acquiring DCI from the PDCCH. When the bundling information indicates a first value, the UE may perform bundling such that only REGs locating on a same RB and corresponding to different OFDM symbols in the CORESET, are bundled as 1 REG bundle, and when the bundling information indicates a second value, the UE may perform bundling such that the REGs locating on the same RB and corresponding to the different OFDM symbols are bundled as 1 REG bundle along with REGs locating on different RBs in the CORESET, and the UE may perform the blind detection of the PDCCH by assuming same precoding for REGs belonging to a same REG bundle as a result of REG bundling.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/064,754, filed on Jun. 21, 2018, now allowed, which is a NationalStage application under 35 U.S.C. § 371 of International Application No.PCT/KR2018/004725, filed on Apr. 24, 2018, which claims the benefit ofU.S. Provisional Application No. 62/519,157, filed on Jun. 13, 2017, andU.S. Provisional Application No. 62/489,419, filed on Apr. 24, 2017. Thedisclosures of the prior applications are incorporated by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting andreceiving a downlink (DL) control information in a wirelesscommunication system.

BACKGROUND

First, the existing 3GPP LTE/LTE-A system will be briefly described.Referring to FIG. 1, the UE performs an initial cell search (S101). Inthe initial cell search process, the UE receives a PrimarySynchronization Channel (P-SCH) and a Secondary Synchronization Channel(S-SCH) from a base station, performs downlink synchronization with theBS, and acquires information such as a cell ID. Thereafter, the UEacquires system information (e.g., MIB) through a PBCH (PhysicalBroadcast Channel). The UE can receive the DL RS (Downlink ReferenceSignal) and check the downlink channel status.

After the initial cell search, the UE can acquire more detailed systeminformation (e.g., SIBs) by receiving a Physical Downlink ControlChannel (PDCCH) and a Physical Downlink Control Channel (PDSCH)scheduled by the PDCCH (S102).

The UE may perform a random access procedure for uplink synchronization.The UE transmits a preamble (e.g., Msg1) through a physical randomaccess channel (PRACH) (S103), and receives a response message (e.g.,Msg2) for the preamble through PDCCH and PDSCH corresponding to thePDCCH. In the case of a contention-based random access, a contentionresolution procedure such as additional PRACH transmission (S105) andPDCCH/PDSCH reception (S106) may be performed.

Then, the UE can perform PDCCH/PDSCH reception (S107) and PhysicalUplink Shared Channel (PUSCH)/Physical Uplink Control Channel (PUCCH)transmission (S108) as a general uplink/downlink signal transmissionprocedure. The UE can transmit UCI (Uplink Control Information) to theBS. The UCI may include HARQ ACK/NACK (Hybrid Automatic Repeat reQuestAcknowledgment/Negative ACK), SR (Scheduling Request), CQI (ChannelQuality Indicator), PMI (Precoding Matrix Indicator) and/or RI etc.

SUMMARY

An object of the present invention devised to solve the problem lies ina method and apparatus for more effectively and accurately transmittingor receiving downlink control information through resource element group(REG) bundling in wireless communication system.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

In an aspect of the present invention to achieve the object of thepresent invention, a method of receiving downlink control information bya user equipment (UE) in a wireless communication system, includesreceiving, via higher layer signaling, bundling information regardingresource element groups (REGs), each of the REGs corresponding to 1resource block (RB) and 1 orthogonal frequency divisional multiplexing(OFDM) symbol; performing blind detection for a physical downlinkcontrol channel (PDCCH) in a control resource set (CORESET) configuredon a plurality of OFDM symbols; and acquiring downlink controlinformation (DCI) from the blind-detected PDCCH, wherein in the blinddetection for the PDCCH, when the bundling information indicates a firstvalue, the UE may perform bundling such that only REGs locating on asame RB and corresponding to different OFDM symbols in the CORESET, arebundled as 1 REG bundle, and when the bundling information indicates asecond value, the UE may perform bundling such that the REGs locating onthe same RB and corresponding to the different OFDM symbols are bundledas 1 REG bundle along with REGs locating on different RBs in theCORESET, and wherein the UE may perform the blind detection of the PDCCHby assuming same precoding for REGs which belong to a same REG bundle asa result of REG bundling.

In other aspect of the present invention, a method of transmittingdownlink control information by a base station (BS) in a wirelesscommunication system, includes transmitting, via higher layer signaling,bundling information regarding resource element groups (REGs), each ofthe REGs corresponding to 1 resource block (RB) and 1 orthogonalfrequency divisional multiplexing (OFDM) symbol; and transmittingdownlink control information (DCI) through a physical downlink controlchannel (PDCCH) in a control resource set (CORESET) configured on aplurality of OFDM symbols, wherein in transmitting the DCI, when thebundling information indicates a first value, the BS may performbundling such that only REGs locating on a same RB and corresponding todifferent OFDM symbols in the CORESET, are bundled as 1 REG bundle, whenthe bundling information indicates a second value, the BS may performbundling such that the REGs locating on the same RB and corresponding tothe different OFDM symbols are bundled as 1 REG bundle along with REGslocating on different RBs in the CORE SET, and wherein the BS maytransmit the DCI by applying same precoding for REGs belonging to a sameREG bundle as a result of REG bundling.

In another aspect of the present invention, a user equipment (UE) forreceiving downlink control information, includes a receiver; and aprocessor to receive, via higher layer signaling by using the receiver,bundling information regarding resource element groups (REGs), each ofthe REGs corresponding to 1 resource block (RB) and 1 orthogonalfrequency divisional multiplexing (OFDM) symbol, to perform blinddetection for a physical downlink control channel (PDCCH) in a controlresource set (CORESET) configured on a plurality of OFDM symbols, and toacquire downlink control information (DCI) from the blind-detectedPDCCH, wherein in the blind detection for the PDCCH, when the bundlinginformation indicates a first value, the processor may perform bundlingsuch that only REGs locating on a same RB and corresponding to differentOFDM symbols in the CORESET, are bundled as 1 REG bundle, and when thebundling information indicates a second value, the processor may performbundling such that the REGs locating on the same RB and corresponding tothe different OFDM symbols are bundled as 1 REG bundle along with REGslocating on different RBs in the CORESET, and wherein the processor mayperform the blind detection of the PDCCH by assuming same precoding forREGs which belong to a same REG bundle as a result of REG bundling.

In another aspect of the present invention, a base station (B S) fortransmitting downlink control information, includes a transmitter; and aprocessor to transmit, via higher layer signaling by using thetransceiver, bundling information regarding resource element groups(REGs), each of the REGs corresponding to 1 resource block (RB) and 1orthogonal frequency divisional multiplexing (OFDM) symbol, and totransmit downlink control information (DCI) through a physical downlinkcontrol channel (PDCCH) in a control resource set (CORESET) configuredon a plurality of OFDM symbols, wherein in the transmission of the DCI,when the bundling information indicates a first value, the processor mayperform bundling such that only REGs locating on a same RB andcorresponding to different OFDM symbols in the CORESET, are bundled as 1REG bundle, when the bundling information indicates a second value, theprocessor may perform bundling such that the REGs locating on the sameRB and corresponding to the different OFDM symbols are bundled as 1 REGbundle along with REGs locating on different RBs in the CORESET, andwherein the processor may transmit the DCI by applying same precodingfor REGs belonging to a same REG bundle as a result of REG bundling.

When the bundling information indicates the first value, 1 REG bundlesize may be configured to be the same as the number of the plurality ofOFDM symbols for configuring the CORESET.

When the bundling information indicates the second value, 1 REG bundlesize may be configured to be the same as the number of REGs included in1 control channel element (CCE).

One or more CORESETs including the CORESET may be configured in the UE.The bundling information and a control channel element (CCE)-to-REGmapping type may be indicated for each of the one or more CORESETs.

The bundling information may include bundle size information indicatingthe number of REGs included in 1 REG bundle.

The control channel element (CCE)-to-REG mapping type of the CORESET maybe configured as an interleaved mapping type among a localized mappingtype and the interleaved mapping type.

Interleaving for the CCE-to-REG mapping may be performed in a unit of aREG bundle using an REG bundle index.

A supported bundle size may be differently determined according to theCCE-to-REG mapping type.

The bundling information may include at least one of intra-CCE bundlesize information for bundling of REGs belonging to the same controlchannel element (CCE) and inter-CCE bundle size information for bundlingof REGs belonging to different control channel elements (CCEs). When thebundling information includes the inter-CCE bundle size information, theUE may perform blind detection for the PDCCH by assuming the sameprecoding for REGs of different CCEs belonging to the same inter-CCEbundle.

When the bundling information indicates the first value, the UE mayperform time domain REG bundling and, when the bundling informationindicates the second value, the UE may perform time-frequency domain REGbundling.

The number of the plurality of OFDM symbols for configuring the CORESETmay be 2 or 3.

The UE may perform demodulation for the PDCCH by assuming that the sameprecoding is applied to reference signals received through REGsbelonging to the same REG bundle.

According to an embodiment of the present invention, a user equipment(UE) performs time domain bundling or time-frequency domain bundlingaccording to indication of a network and assumes the same precoding withrespect to a plurality of resource element groups (REGs) belonging to 1REG bundle and, thus, detection for a physical downlink control channel(PDCCH) carrying downlink control information (DCI) may be moreaccurately and effectively performed.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates physical channels used in a 3GPP LTE/LTE-A system anda general signal transmission method using the physical channels.

FIG. 2 illustrates an NR control region according to an embodiment ofthe present invention.

FIG. 3 illustrates frequency domain bundling according to an embodimentof the present invention.

FIG. 4 illustrates a time domain bundling type according to anembodiment of the present invention.

FIG. 5 illustrates channel estimation performance of time domainbundling according to an embodiment of the present invention.

FIG. 6 illustrates bundling options according to an embodiment of thepresent invention.

FIG. 7 illustrates a CORESET and a sub-CORESET according to anembodiment of the present invention.

FIG. 8 is a diagram for explanation of resource indexing according to anembodiment of the present invention.

FIG. 9 is a diagram for explanation of a method of indicating the sameprecoding pattern according to an embodiment of the present invention.

FIG. 10 illustrates RS patterns for adjusting RS patterns for adjustingRS density according to an embodiment of the present invention.

FIG. 11 illustrates the case in which CORESETs with different CORESETdurations overlap with each other according to an embodiment of thepresent invention.

FIG. 12 illustrates a flow of a method of transmitting and receivingdownlink control information (DCI) according to an embodiment of thepresent invention.

FIG. 13 illustrates a base station (BS) and a user equipment (UE)according to an embodiment of the present invention.

DETAILED DESCRIPTION

The following description of embodiments of the present invention mayapply to various wireless access systems including CDMA (code divisionmultiple access), FDMA (frequency division multiple access), TDMA (timedivision multiple access), OFDMA (orthogonal frequency division multipleaccess), SC-FDMA (single carrier frequency division multiple access) andthe like. CDMA can be implemented with such a radio technology as UTRA(universal terrestrial radio access), CDMA 2000 and the like. TDMA canbe implemented with such a radio technology as GSM/GPRS/EDGE (GlobalSystem for Mobile communications)/General Packet Radio Service/EnhancedData Rates for GSM Evolution). OFDMA can be implemented with such aradio technology as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, E-UTRA (Evolved UTRA), etc. UTRA is a part of UMTS (UniversalMobile Telecommunications System). 3GPP (3rd Generation PartnershipProject) LTE (long term evolution) is a part of E-UMTS (Evolved UMTS)that uses E-UTRA. 3GPP LTE adopts OFDMA in downlink and adopts SC-FDMAin uplink. LTE-A (LTE-Advanced) is an evolved version of 3GPP LTE.

For clarity, the following description mainly concerns 3GPP LTE systemor 3GPP LTE-A system, by which the technical idea of the presentinvention may be non-limited. Specific terminologies used in thefollowing description are provided to help understand the presentinvention and the use of the terminologies can be modified to adifferent form within a scope of the technical idea of the presentinvention.

As many as possible communication devices have demanded as high ascommunication capacity and, thus, there has been a need for enhancedmobile broadband (eMBB) communication compared with legacy radio accesstechnology (RAT) in a recently discussed next-generation communicationsystem. In addition, massive machine type communications (mMTC) forconnecting a plurality of devices and objects to provide variousservices anytime and anywhere is also one of factors to be considered innext-generation communication. In addition, in consideration of aservice/UE that is sensitive to reliability and latency, ultra-reliableand low latency communication (URLLC) has been discussed for anext-generation communication system.

As such, new RAT that considers eMBB, mMTC, URLCC, and so on has beendiscussed for next-generation wireless communication.

Some LTE/LTE-A operations and configuration that are not at variance toa design of New RAT may also be applied to new RAT. For convenience, newRAT may be referred to as 5G mobile communication.

<NR Frame Structure and Physical Resource>

In an NR system, downlink (DL) and downlink (UL) transmission may beperformed through frames having duration of 10 ms and each frame mayinclude 10 subframes. Accordingly, 1 subframe may correspond to 1 ms.Each frame may be divided into two half-frames.

1 subframe may include N_(symb) ^(subframe,μ)=N_(symb) ^(slot)×N_(slot)^(subframe,μ) contiguous OFDM symbols. N_(symb) ^(slot) represents thenumber of symbols per slot, t represents OFDM numerology, and N_(slot)^(subframe,μ) represents the number of slots per subframe with respectto corresponding μ. In NR, multiple OFDM numerologies shown in Table 1below may be supported.

TABLE 1 μ Δf = 2^(μ) · 15 [kHz] Cyclic prefix 0 15 Normal 1 30 Normal 260 Normal, Extended 3 120 Normal 4 240 Normal

In Table 1 above, Δf refers to subcarrier spacing (SCS). μ and cyclicprefix with respect to a DL carrier bandwidth part (BWP) and μ andcyclic prefix with respect to a UL carrier BWP may be configured for aUE via UL signaling.

Table 2 below shows the number of N_(symb) ^(slot) of symbols per slot,the number N_(slot) ^(frame,μ) of symbols per frame, and the numberN_(slot) ^(subframe,μ) of slots per subframe with respect to each SCS inthe case of normal CP.

TABLE 2 μ N_(symb) ^(slot) N_(slot) ^(frame, μ) N_(slot) ^(subframe, μ)0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16 5 14 320 32

Table 3 below shows the number N_(symb) ^(slot) of symbols per slot, thenumber N_(slot) ^(frame,μ) of slots per frame, and the number N_(slot)^(subframe,μ) of slots per subframe with respect to each SCS in the case of extended CP.

TABLE 3 μ N_(symb) ^(slot) N_(slot) ^(frame, μ) N_(slot) ^(subframe, μ)2 12 40 4

As such, in an NR system, the number of slots included in 1 subframe maybe changed according to subcarrier spacing (SCS). OFDM symbols includedin each slot may correspond to any one of D (DL), U (UL), and X(flexible). DL transmission may be performed in a D or X symbol and ULtransmission may be performed in a U or X symbol. A Flexible resource(e.g., X symbol) may also be referred to as a Reserved resource, anOther resource, or a Unknown resource.

In NR, one resource block (RB) may correspond to 12 subcarriers in thefrequency domain. A RB may include a plurality of OFDM symbols. Aresource element (RE) may correspond to 1 subcarrier and 1 OFDM symbol.Accordingly, 12 REs may be present on 1 OFDM symbol in 1 RB.

A carrier BWP may be defined as a set of contiguous physical resourceblocks (PRBs). The carrier BWP may also be simply referred to a BWP. Amaximum of 4 BWPs may be configured for each of UL/DL link in 1 UE. Evenif multiple BWPs are configured, 1 BWP may be activated for a given timeperiod. However, when a supplementary uplink (SUL) is configured in aUE, 4 BWPs may be additionally configured for the SUL and 1 BWP may beactivated for a given time period. A UE may not be expected to receive aPDSCH, a PDCCH, a channel state information-reference signal (CSI-RS),or a tracking reference signal (TRS) out of the activated DL BWP. Inaddition, the UE may not be expected to receive a PUSCH or a PUCCH outof the activated UL BWP.

<NR DL Control Channel>

In an NR system, a transmissions NR system, a transmission unit of acontrol channel may be defined as a resource element group (REG) and/ora control channel element (CCE), etc. The CCE may refer to a minimumunit for control channel transmission. That is, a minimum PDCCH size maycorrespond to 1 CCE. When an aggregation level is equal to or greaterthan 2, a network may group a plurality of CCEs to transmit one PDCCH(i.e., CCE aggregation).

An REG may correspond to 1 OFDM symbol in the time domain and maycorrespond to 1 PRB in the frequency domain. In addition, 1 CCE maycorrespond to 6 REGs.

A control resource set (CORESET) and a search space (SS) are brieflydescribed now. The CORESET may be a set of resources for control signaltransmission and the search space may be aggregation of control channelcandidates for perform blind detection. The search space may beconfigured for the CORESET. For example, when one search space isdefined on one CORESET, a CORESET for a common search space (CSS) and aCORESET for a UE-specific search space (USS) may each be configured. Asanother example, a plurality of search spaces may be defined in oneCORESET. For example, the CSS and the USS may be configured for the sameCORESET. In the following example, the CSS may refer to a CORESET with aCSS configured therefor and the USS may refer to a CORESET with a USSconfigured therefor, or the like.

An eNB may signal information on a CORESET to a UE. For example, aCORESET configuration for each CORESET may be signaled to the UE, andthe CORESET configuration may be signaled in time duration (e.g., 1/2/3symbol), etc. of the corresponding CORESET. Information included in theCORESET configuration is described below in detail.

<Bundling for NR-PDCCH>

Prior to a description of resource bundling in an NR system, physicalresource block (PRB) bundling in a legacy LTE system is describedbriefly. When a DMRS with lower density than a cell specific RS (CRS) isused in an LTE system, an available resource is increased for datatransmission but, as the number of available RSs for channel estimationis increased, channel estimation performance may be degraded. As such,to minimize degradation in channel estimation performance during DMRSuse, PRB bundling is introduced in an LTE system. For ex ample, toensure channel estimation performance in a transmission mode in which aDMRS is used, sections in which the same precoding is applied may bedefined as a PRB bundle and, in the corresponding sections, a UE mayperform channel estimation using RSs belonging to different PRBs. Forexample, DMRS 2 mapped to PRB 2 as well as DMRS 1 mapped to PRB 1 may beused for channel estimation of demodulation of data mapped to PRB 1. Forvalid channel estimation in units of PRB bundles, the same precodingneeds to be applied to DMRS 1 and DMRS 2.

To enhance system flexibility in NR, reduction in use of a common RS hasbeen discussed. The common RS may be a cell-commonly transmitted RS andmay refer to an always on RS that is not capable of being on/offUE-specifically. For example, a cell-specific RS (CRS) of an LTE systemmay be an example of the common RS.

A design for reduction in the common RS is also applied to a controlchannel (e.g., PDCCH) of NR and, thus, it may be desirable to performbundling between different control channel resources to enhance channelestimation performance of a control channel.

Hereinafter, it is assumed that 1 REG=1 PRB & 1 OFDM symbol, and 1 CCE=6REGs but the present invention is not limited thereto and the presentinvention may also be applied to the case in which various resourceunits, e.g., REG, CCE, and PDCCH candidate are configured usingdifferent methods. As another example of definition of an REG, 1 REG maycorrespond to 12 contiguous resource elements (REs) in the frequencydomain and the number of REs used for control information transmissionmay be changed according to whether an RS is included in thecorresponding REG and/or whether a reserved resource is present.

Hereinafter, the RS may include an RS for demodulation of a controlchannel, an RS for positioning, CSI-RS for CSI feedback, an interferencemeasurement resource (IMR), a cell-specific tracking RS (e.g., phasetracking), a radio link monitoring (RLM)-RS, and/or radio resourcemanagement (RRM)-RS, etc. and for convenience of description, thepresent invention is mainly described in terms of an RS for demodulationof a control channel.

FIG. 2 illustrates a NR control region according to an embodiment of thepresent invention.

A CORESET may correspond to a region in which REG/CCE indexing isperformed. 1 UE may be configured with one or more CORESETs from anetwork. When a plurality of CORESETs is configured for 1 UE, therespective CORESETs may have different properties. For example, aCCE-to-REG mapping type, a PDCCH-to-CCE mapping type, and/or an RSconfiguration, etc. for each CORESET may be defined via high layersignaling (e.g., CORESET configuration).

Although FIG. 2 illustrates only CORESET duration in the time domain, arange of a CORESET may also be configured in the frequency domain.

Bundling of an REG level may be applied to an NR control channel. Whenthe bundling of an REG level is applied, the same precoding may beapplied to different REGs belonging to the same bundle.

When different REGs belonging to the same bundle belongs to 1 CCE, suchREG bundling may be defined as intra-CCE REG bundling. When differentREGs belonging to the same bundle belongs to different CCEs, such REGbundling may be defined as inter-CCE bundling.

Hereinafter, a method of performing bundling on an NR control channel isproposed. In the following examples, 1 CCE=6 REGs is assumed but thepresent invention may also be applied to the case in which the number ofREGs per CCE may be differently defined.

REG bundling in an NR control channel may be defined in the frequencydomain and/or the time domain. An operating method, etc. of a UE and aneNB for bundling in each domain is described below.

Frequency Domain Bundling

In terms of a network, frequency domain REG bundling may apply the sameprecoding to different REGs on the same time instance. A UE may performchannel estimation using RSs on different REGs belonging to the samebundle, thereby enhancing channel estimation performance.

FIG. 3 illustrates an example of frequency domain bundling.

R refers to an RE in which a reference signal is transmitted, D refersto an RE in which control information is transmitted, and X refers to anRE in which an RS of another antenna port is transmitted.

When a bundle size is 1 REG (i.e., when REG bundling is not applied),channel estimation for each RE in which control information istransmitted may be performed using an RS in a corresponding REG. When abundle size is 2 REGs, channel estimation for each RE in which controlinformation is transmitted may be performed using all RS(s) present inthe bundle size.

Accordingly, when a bundle size is greater than 1 REG, a UE may performchannel estimation using as many as possible RS(s) to enhance channelestimation performance.

In the case of frequency domain bundling, it may be desirable todifferently configure a size of bundling according to a resource mappingtype of a CORESET in which bundling is performed. For example, when aCCE-to-REG mapping method indicted through a CORESET configuration isdistributed mapping (e.g., interleaving), a bundle size may bedetermined in consideration of both channel estimation performance andfrequency diversity gain. When the frequency diversity gain determinesoverall performance compared with the channel estimation performance, itmay be desirable not to perform bundling for enhancing the channelestimation performance or maintain a bundle size in a small value (e.g.,2 REGs). On the other hand, when the channel estimation performance ismore important than acquisition of the frequency diversity gain, it maybe desirable to configure the bundle size as a large value (e.g., 3REGs) to enhance the channel estimation performance.

As such, to adaptively correspond to various channel environments, anetwork may configure a bundle size for each specific resource region(e.g., CORESET). For example, an REG bundle size for each CORESET may beindicated to a UE via higher layer signaling (e.g., CORESETconfiguration), etc.

In the case of localized mapping, it may be desirable to support a largebundle size (e.g., maximum REG bundle size). The bundle size of thelocalized mapping may be more largely configured than a bundle size ofthe distributed mapping.

Use of the localized mapping may mean that a network applies appropriateprecoding to a UE due to relatively accurate channel information betweenthe network and the UE. In this case, the network may deploy all REGsconfiguring a CCE to be adjacent to each other in the frequency domainand may apply the same precoding to REGs. For example, in the case ofnon-Interleaved (i.e. localized) CCE-to-REG mapping, 1 CCE maycorrespond to an REG bundle. In other words, an REG bundle size may alsobe fixed to 1 CCE (i.e., 6 REGs) during localized mapping.

According to an embodiment of the present invention, signaling ofdifferent bundle sizes according to a resource mapping type (i.e.,REG-to-CCE mapping type) by a network with respect to frequency domainbundling is proposed. A supported bundle size may be determinedaccording to an REG-to-CCE mapping type. For example, in localizedmapping, an REG bundle size may be fixed to 6-REG and, in distributedmapping (e.g., interleaving), a network may configure an REG bundle sizefor a UE via higher layer signaling (e.g., CORESET configuration).

Signaling of different bundle sizes according to a resource mapping typeby a network may mean that a maximum value of a bundle size for eachresource mapping type (e.g., localized/distributed mapping) isdifferently configured. For example, when the number of bits forsignaling a bundle size is equalized in both localized/distributedmappings (e.g., when the number of available bundle sizes is constantirrespective of a resource mapping type), a bundle size indicated by acorresponding bit value may be differently defined according to aresource mapping method. For example, assuming that a bundle size isindicated by 1 bit, 1 Bit=0/1 may represent bundle size=2/3 REGs in thedistributed mapping, and 1 Bit=0/1 may represent bundle size=3/6 REGs inthe localized mapping.

Another bundle size may also be defined for inter-CCE bundling. Forexample, the aforementioned bundle size may refer to an intra-CCE bundlesize, and a maximum bundle size may be additionally defined forinter-CCE bundling separately from an intra-CCE bundle size. When REGsbelonging to different CCEs are positioned adjacently to each other, anetwork may perform frequency domain bundling on REGs positioned in amaximum bundle size. As such, a maximum bundling size for the inter-CCEbundling may refer to a distance between REGs in which the inter-CCEbundling is permissible. For example, the maximum bundling size may bedefined on the frequency domain. For example, the maximum bundling sizemay be defined on the frequency domain and/or the time domain.

A first bundle size for the intra-CCE bundling and a second bundle sizefor the inter-CCE bundling may be independently signaled. A network/UEmay perform REG indexing/CCE indexing, etc. based on a first bundle sizeor the like in the intra-CCE bundling and may perform the inter-CCEbundling on REGs belonging to different CCEs in the second bundle sizeafter CCE aggregation. The second bundle size for the inter-CCE bundlingmay be configured as a value for including a predetermined number ofintra-CCE REG bundle(s). For example, the second bundle size may bedetermined an integer multiple of the first bundle size. For example,when the intra-CCE bundling is performed in units of 2-REG (e.g., firstbundle size=2-REG) and the second bundle size for the inter-CCE bundlingis configured as 4-REG, a UE may assume the same precoding with respectto 2 intra-CCE REG bundles (i.e., total of 4 REGs) belonging todifferent CCEs and may perform channel estimation.

Alternatively, the UE may assume that a PRB bundle size configured in adata (e.g., PDSCH) region is also applied to a control channel. Suchassumption may be applied to both cases in which REGs present in acorresponding bundle size are contiguous or noncontiguous and may alsobe applied to intra-CCE and/or inter-CCE.

For example, assuming that 6-REG is mapped to 1 CCE via localizedmapping and 4-RB configures 1 bundle in the case of a PDSCH, theintra-CCE REG bundle size or the inter-CCE bundle size may be configuredas 4. For example, assuming that 2 CCEs (e.g., CCE #0 and CCE #1) for anaggregation level (AL)-2 channel candidate are contiguous in thefrequency domain, REG bundling may be performed according to [firstbundle: 4-REG of CCE #0]+[second bundle: 2-REG of CCE #0 & 2-REG of CCE#1]+[third bundle: 4-REG of CCE #1].

To apply an REG bundle on the frequency domain, it may be required todetermine a boundary at which an REG bundle is started/ended. Forexample, as described in (i) to (v), a boundary of an REG bundle may bedetermined. When methods of (i) or (iv) is used, it may be desirable toconfigure a bandwidth or PRB number configured for a UE as a multiple ofa bundle size.

(i) A bundle size may be applied from a lowest frequency (e.g., lowestsubcarrier) in a CORESET configured for a UE. For example, REG indexingand/or REG bundle indexing may be used for each CORESET and, wheninterleaving is used, interleaving may be performed in units of REGbundles. When a reserved resource is present in a bundle size or a PRBthat is not allocated to a UE is present, an actual bundle size of theUE may be smaller than a bundle size indicated from a network.

(ii) A bundle size may be applied from a lowest frequency in aUE-specific bandwidth configured for the UE. When a reserved resource ispresent in a bundle size or a PRB that is not allocated to the UE ispresent, an actual bundle size of the UE may be smaller than a bundlesize indicated from a network.

(iii) A bundle size may be applied from a lowest frequency in an entiresystem bandwidth. When a reserved resource is present in a bundle sizeor a PRB that is not allocated to the UE is present, an actual bundlesize of the UE may be smaller than a bundle size indicated from anetwork.

(iv) The frequency domain to which an REG bundle is to be applied may beseparately configured and a bundle size may be applied from a lowestfrequency in the corresponding frequency domain. When a reservedresource is present in a bundle size or a PRB that is not allocated tothe UE is present, an actual bundle size of the UE may be smaller than abundle size indicated from a network.

(v) The UE may consider a starting point of a control channel candidateas a position where REG bundling is started. For example, a bundle sizemay be applied from a start CCE or start REG of the candidate. The UEmay assume that the same precoding is applied to corresponding REGs whendifferent REGs belonging to the same candidate are present in a bundlesize. When REGs belonging to the candidate are distributed to differentgroups, the UE may consider a starting point of each group as a startingpoint of a bundle.

When a precoder cycling in which precoding is cyclically changed everyspecific resource unit, or the like is used, bundling may be performedin the same resource unit as the resource unit in which the precodercycling is applied. For example, assuming that 2 precoders arecyclically applied on contiguous REGs, even index REGs may be bundledand odd index REGs may be bundled. This may be understood as bundling atan REG group (e.g., even REG group/odd REG group) level. For example,REGs to which Precoder 1 is applied may correspond to a first REG groupbundle and REGs to which Precoder 2 is applied may correspond to asecond REG group bundle. In this case, even if precoder cycling is used,the UE may assume the same precoding with respect to REGs belonging tothe same bundle.

When REG bundling and precoder cycling are used together, the REGbundling may not be always performed on contiguous REGs. For example,noncontiguous REGs may belong to the same REG bundle. In this case, a UEmay be allocated with an REG or RB bundle size from a network and one ormore precoders may be present in the allocated REG/RB bundle size. TheUE may be configured with the number of precoders in the REG/RB bundlesize from a network. The number of precoders in the REG/RB bundle sizemay be different according to a method of configuring precoder cycling.

-   -   Configuration of precoder cycling with REG/RB bundle size: For        example, to perform precoder cycling every RB/REG (e.g., to        change a precoder in units of RB/REGs), a network may configure        a bundle size as 1.    -   Configuration of REG bundle along with configuration of precoder        cycling: A network may allocate an REG bundle size and the        number of precoders to be used in each bundle to the UE.        Assuming that 2 precoders cycle in a 6-RB bundle, the network        may perform precoder cycling in units of 1 REG/RB and, in this        case, 3 RBs may share the same precoder.

Time-Domain Bundling

Similarly to frequency domain bundling, the same precoding may also beapplied to REGs in a bundle size in the case of time domain bundling.

According to a method of applying the same precoding, time domainbundling may be differently defined. According to an embodiment of thepresent invention, the time domain bundling may be defined as two typesas follows and a network may signal a type of time domain bundling, tobe used for each resource region (e.g., CORESET, sub-CORESET).

(1) Time Domain Bundling Type 1: When RS is Transmitted in all REGs inBundle

Type 1 bundling may be used to enhance channel estimation performance.To enhance channel estimation, each of REGs in the time domain bundlesize may include an RS. Density of the RS may be different for each REG.For example, density of an RS mapped to an REG of a first OFDM symboland density of an RS mapped to an REG of a second OFDM symbol may bedifferent.

As one of available operations of a UE with respect to Type 1 bundling,channel estimation may be performed using all RSs in a bundle. Forexample, to obtain a channel coefficient of a specific data RE through2D-minimum mean square error (MMSE)-based channel estimation, the UE mayuse all RSs in a bundle to which the specific data RE belongs. In thiscase, similarly to the frequency domain bundling, the UE may performchannel estimation using a plurality of RSs to enhance channelestimation performance.

As another operation of a UE that performs Type 1 bundling, the UE mayperforms channel estimation for each REG and, in this case, may use anaverage of channel estimation results of REGs in a bundle as a finalchannel estimation result. In this case, when REGs in a bundle arepresent in a coherent time and channel variation barely occurs, noisemay be suppressed.

(2) Time Domain Bundling Type 2: When RS is Transmitted Only in REG inBundle (e.g., RS of Front-Loaded REG)

Type 2 bundling may be used as a method of reducing RS overhead toacquire coding gain of control information. When Type 2 bundling isused, a network may transmit an RS only some REGs of REGs in a bundleand may map control information to an RE position from which an RS isomitted in the other REGs in which an RS is not transmitted, therebylowering a coding rate of the control information.

In Type 2 bundling, a UE may perform channel estimation in an REG inwhich an RS is transmitted and may reuse a channel estimation resultwith respect to an REG in which an RS is not transmitted. Such reuse ofthe channel estimation result may be based on REG bundling definitionfor applying the same precoding to REGs in a bundle.

FIG. 4 illustrates time domain bundling Types 1/2 according to anembodiment of the present invention. R refers to an RE in which an RS istransmitted and D refers to an RE in which control information istransmitted. RSs of the same antenna port may be mapped to all RS REs orRSs of different antenna ports may be multiplexed and mapped using anFDM/CDM method.

As described above, time domain REG bundling may be defined as Types 1/2and a network may apply/signal different types of time domain bundlingfor respective resource regions.

As another example, when a specific condition is satisfied, applicationof a specific type of time domain bundling may also be predefined.

FIG. 5 illustrates channel estimation performance of time domainbundling according to an embodiment of the present invention. Thechannel estimation performance illustrated in FIG. 5 is a resultobtained under assumption that distributed mapping is applied to acandidate of aggregation level 2 and indicates performance when eachtype of time domain is applied to various transport block sizes (TBSs).

A coding rate according to each type and each TBS in FIG. 5 may be(Type1, 36 bits)=0.1875, (Type1, 76 bits)=0.3958, (Type1, 100bits)=0.5208, (Type2, 36 bits)=0.15, (Type2, 76 bits)=0.3167, and(Type2, 100 bits)=0.4167.

Comparing the experimental result depending on a coding rate withrespect to each case, it may be seen that, when a coding rate is high,time bundling of Type 2 is appropriate and, when a coding rate is low,time bundling of Type 1 is appropriate.

In other words, when a coding rate is low, this means that channelestimation performance largely affects overall performance and, when acoding rate is high, coding gain largely affects overall performance.

Based on the experimental result, a configuration of different domainbundling types depending on a coding rate (e.g., for each aggregationlevel, for each DCI format, for each payload size, and/or for eachcoding rate in consideration of reserved resource) may be proposed. Forexample, a coding rate-specific time bundling type may be defined. Atime domain bundling type for each aggregation level may be determinedby a network or may be determined for each DCI format or payload size.

To enhance system flexibility, a network/UE may divide candidates in aresource region in which time domain bundling is applied to distributethe candidates to time bundling types. For example, when the UE needs toperform blind decoding on 4 AL-1 candidates, 4 AL-2 candidates, 2 AL-4candidates, and 2 AL-8 candidates, the UE may perform blind decodingassuming Type 1 time bundling with respect to a half of the candidatesof each AL and Type 2 time bundling with respect to the other half ofthe candidate. For such an operation of the UE, a network may indicate acandidate for which Type 1 needs to be assumed and a candidate for whichType 2 needs to be assumed in a resource region in which time domainbundling is performed, via higher layer signaling or the like.

When an aggregation level of a candidate is differently configured foreach resource region (e.g., CORESET), a time domain bundling type of acorresponding resource region may be determined according to anaggregation level. For example, when CORESET 0 and CORESET 1 areconfigured for a UE, only a candidate for ALs 1 and 2 is present inCORESET 0, and only a candidate for ALs 4 and 8 are present in CORESET1, the UE may perform blind decoding assuming Type 2 time domainbundling with respect to CORESET 0 and Type 1 time domain bundling withrespect to CORESET 1.

In addition, a type of time bundling may be determined depending onspeed of a UE. Type 1 time domain bundling is more robust to a rapidchannel change in the time domain than Type 2 time domain bundling.Based on speed, a Doppler frequency, or the like of the UE, a timedomain bundling type may also be determined. To this end, the UE mayperiodically (or aperiodically) notify the network about the speed, theDoppler frequency, or the like.

When time domain REG bundling and frequency domain REG bundling aresimultaneously applied, an RS configuration may be determined accordingto a time domain REG bundling type. When only the frequency domain REGbundling is applied, the RS may be transmitted in all REGs or an REG inwhich the RS is transmitted may be determined by a network.

Intra-CCE Bundling

Intra-CCE bundling may refer to bundling of REGs included in 1 CCE and,aforementioned time and/or frequency domain REG bundling can be appliedto the intra-CCE bundling.

For a specific resource region (e.g., CORESET), network may indicate, toa UE via higher layer signaling etc., one of all or some of options (i)to (iii) below or one of all or some of options (i) to (iii) below maybe predefined. For example, the network may signal at least one ofoptions (i) to (iii) to the UE through a CORESET configuration.

(i) Whether time domain REG bundling is applied and/or bundle size:Information indicating whether time domain REG bundling is applied in aspecific resource region and/or a bundle size may be transmitted vianetwork signaling etc., or may be predefined. The information indicatingwhether the time domain REG bundling is applied may be replaced withsignaling of a bundle size.

(ii) Whether frequency domain REG bundling is applied and/or bundlesize: Information indicating whether frequency domain REG bundling isapplied in a specific resource region and/or a bundle size may betransmitted via network signaling etc., or may be predefined. Theinformation indicating whether the frequency domain REG bundling isapplied may be replaced with signaling of a bundle size.

(iii) Whether time and frequency domain REG bundling is applied and/orbundle size: Time domain REG bundling and frequency domain REG bundlingmay be simultaneously applied. Information indicating whether time andfrequency domain REG bundling are applied in a specific resource regionmay be transmitted via network signaling etc., or may be predefined. Theinformation indicating whether the time and frequency domain REGbundling are applied in the region may be replaced with signaling of abundle size for each domain.

A method of replacing the information indicating whether time/frequencydomain REG bundling is applied with signaling of a bundle size isdescribed now in more detail. When an REG bundle size is equal to orgreater than 2 REGs, it may be interpreted as REG bundling is to beapplied. In this case, whether the REG bundling to be appliedcorresponds to time domain bundling, frequency domain bundling, ortime-frequency domain bundling may be determined through a bundle size.For example, when a bundle size of 2 or greater is configured in aspecific resource region (e.g., CORESET) with duration of 1 symbol, itmay be interpreted as frequency domain REG bundling is to be applied.When a bundle size is 2 in a specific resource region (e.g., CORESET)with duration of 2 symbols, it may be interpreted as time domain REGbundling is to be applied and, when a bundle size is equal to or greaterthan 3 (e.g., bundle size=6), it may be interpreted as time-frequencydomain REG bundling is to be applied. When a bundle size is 3 in aspecific resource region (e.g., CORESET) with duration of 3 symbols, itmay be interpreted as time domain REG bundling is to be applied and,when a bundle size is equal to or greater than 4 (e.g., bundle size=6),it may be interpreted as time-frequency domain REG bundling is to beapplied.

More generally, assuming CORESET duration of N-symbol (N being aninteger equal to or greater than 2) and a bundle size of M-REG, in thecase of N≤M, a UE may determine that time domain bundling is applied toa corresponding CORESET and, in the case of N>M, the UE may determinethat time-frequency domain bundling is applied to the correspondingCORESET. When CORESET duration is 1 symbol, REG bundling may alwaysrefer to frequency domain bundling and, in this case, a bundle size mayalso be interpreted to be a size of frequency domain bundling.

FIG. 6 is a diagram showing bundling options according to an embodimentof the present invention.

Referring to FIG. 6, (a) frequency bundling and (b) time bundlingillustrate the case in which a bundle size is 3. (c) time-frequencybundling illustrates the case in which a bundle size is 3 on the timedomain and a bundle size is 2 on the frequency domain. Accordingly, inthe time-frequency bundling, 6 REGs may configure one REG bundle.

In the case of intra-CCE bundling, a bundle size may also be used as abasic unit of resource indexing. For example, when time domain REGbundling is applied in a CORESET in which distributed mapping is used,CORESET duration (i.e., length (symbol number) of a CORESET in the timedomain) may be replaced with a bundle size and a bundle index may beused as a basic unit of distribution (or interleaving). For example, anREG bundle size with the same size as the CORESET duration may besupported. In addition, interleaving may be performed in a unit of a REGbundle.

For example, when a specific CORESET is configured with a combination of100 PRBs & 3 symbols and time domain REG bundling is applied to aspecific CORESET, each PRB may be defined to configure one bundle. Forexample, three contiguous REGs on the time domain, which is positionedin the same frequency resource (i.e., the same PRB) on the frequencydomain, may correspond to one REG bundle. In this case, a network mayinterleave a bundle index of 0 to 99 in a logical domain and may performmapping in a physical domain.

Such a method may also be applied to the frequency domain in the sameway. For example, when a bundle size for frequency domain REG bundlingis signaled to 2 REGs, a UE may assume that two contiguous REGsconfigure one bundle in the frequency domain and may determine resourcemapping or the like when performing blind detection on a correspondingCORESET.

As described in the above embodiments, a size of time domain REGbundling may be determined as a divisor of time domain duration of aresource region (e.g., CORESET) in which bundling is applied. Forexample, assuming four cases in which duration of a resource region inwhich time domain bundling is applied is 1, 2, 3, and 4, a combinationof available time domain bundle sizes with respect to each case may be(1), (1, 2), (1, 3), and (1, 2, 4). In other words, in the case ofresource region duration N=1, 2, 3 symbols, time domain REG bundling maynot be applied (i.e., bundle size=1), or when time domain REG bundlingis applied, a bundle size thereof may be interpreted to be configured tobe the same as duration N of a resource region.

It may be desirable to configure a bundle size as a divisor of durationof a resource region because, when the bundle size is not configured asa divisor of duration of a resource region, the possibility thatdifferent REGs use different frequency resources in 1 bundle needs to beavoided. For example, when time domain bundling is applied in a specificCORESET, bundle size=2 REGs, and duration of a CORESET is 3 symbols,bundle 1 and bundle 3 among bundles configured in a CORESET arepositioned over different PRBs and, thus, time domain bundling may notbe capable of being performed with respect to bundle 1 and bundle 3.

As another example of the present invention, in the case of distributedresource mapping, only one of time/frequency domain REG bundling mayalso be defined to be applied. For example, it may be assumed that bothtime/frequency domain REG bundling are applied to a CCE including 6REGs, a time domain bundle size is 3, and a frequency domain bundle sizeis 2. In this case, to easily perform distribution for acquisition offrequency diversity, a network may perform only REG bundling withrespect to one domain.

In the case of localized resource mapping, application of bothtime/frequency domains bundling or performing of only bundling on onedomain may be configured/predefined by a network. When bothtime/frequency domain bundling are performed, one bundle in which bothbundling in two domains is applied may also be used as a basic unit ofresource indexing.

The above proposed resource region may be a CORESET or a sub-CORESETincluded in the CORESET. sub-CORESETs may be distinguished therebetween.

FIG. 7 illustrates a CORESET and a sub-CORESET according to anembodiment of the present invention.

In (b) of FIG. 7, time domain REG bundling may not be applied and onlyfrequency domain REG bundling may be applied to sub-CORESET0. Timedomain REG bundling of bundle size 2 may be applied to sub-CORESET1.Resource indexing may be independently performed every subCORESET or maybe performed on an entire CORESET or a method for resource indexing maybe indicated by a network via higher layer signaling or the like.

FIG. 8 is a diagram for explanation of resource indexing according to anembodiment of the present invention.

Referring to FIG. 8, (a) sub-CORESET separate indexing may easilyconfigure different search spaces and (b) resource indexing (i.e.,combined indexing) with respect to an entire CORESET may be used as onemethod for simultaneously performing time/frequency domain REG bundling.(a) separate indexing may also be used to distinguish between a searchspace for DCI that needs to be rapidly decoded and a search space forDCI with low limitation in decoding time. Although FIG. 8 illustratesthe case in which resource indexing is performed from a first symbolusing a frequency-first method for convenience, a resource index mayalso be changed by applying interleaving or the like.

Thus far, although bundling between contiguous REGs in thetime/frequency domain has been mainly described, time/frequency REGbundling may be defined by a bundling pattern. For example, when abundling pattern is defined like {2, 1, 2, 1} for frequency domain REGbundling, {REG0, REG1}, {REG2}, {REG3, REG4}, and {REG5} among 6 REGsconfiguring one CCE may each configure an REG bundle.

The bundling pattern may also be used in time domain REG bundling. Forexample, when duration of a resource region in which time domain REGbundling is applied is 3 symbols, a network may signal a bundlingpattern of {2, 1}. A bundling pattern {2, 1} may mean that 2 contiguousREGs configure on bundle and one subsequent REG configures anotherbundle in the time domain. Time bundling Type 1/2 for each bundleincluded in the pattern may be predefined or may be signaled by theabove proposed method.

Inter-CCE Bundling

Like intra-CCE bundling, in the case of inter-CCE bundling, whetherbundling is applied and/or a bundle size may also be signaled by anetwork. The aforementioned REG level bundling related proposals mayalso be applied to CCE level bundling and, in the above proposals, anREG may be replaced with a CCE and inter-CCE bundling may be embodied.

When inter-CCE bundling is embodied using the aforementioned method,there may be additional limitation in a procedure such as resourceindexing. For example, assuming that the inter-CCE bundling is alwaysapplied, an inter-CCE bundle size may need to be assumed and CCEindexing may need to be performed. For example, even if CCE indexes arecontiguous, the inter-CCE bundling may need to be performed on differentCCEs with noncontiguous time/frequency positions and, thus, CCE indexingmay be performed in consideration of a bundle size.

Accordingly, to apply the inter-CCE bundling, a network may configureonly whether the inter-CCE bundling is applied and a bundle size and,when the inter-CCE bundling is applied, a UE may assume the sameprecoding to be applied when contiguous resources are present in thebundle size in the time/frequency domain.

A bundle size for the inter-CCE bundling may be independent from anintra-CCE bundle size. Alternatively, when a maximum bundle size for theinter-CCE bundling is separately defined and REGs belonging to differentCCEs are adjacent to each other, assumption of the same precoding in amaximum bundle size by a UE may be predefined or may be signaled by anetwork.

In addition, inter-CCE bundling in a CORESET to which interleaving isapplied may be replaced with a configuration of an interleaving unitsize. To effectively configure a hierarchical PDDCH structure and/or toreduce blocking probability between CORESETs, interleaving of an REGbundle set unit may be introduced. For example, a network maycontiguously deploy REGs belonging to each CCE configuring a candidatewith a high aggregation level in a CORESET to which interleaving isapplied and may interleave an REG bundle set. When REG bundle set-basedinterleaving is performed and a size of an REG bundle set is configured(for each CORESET), a UE may assume that the size of the REG bundle setis the same as an inter-CCE REG bundle size.

For example, when REG {0, 1, 2, 3, 4, 5} configures CCE0 and REG {6, 7,8, 9, 10, 1} configures CCE1 in 1 symbol CORESET in which interleavingis performed, and CCE0 and CCE1 configure a candidate with aggregationlevel 2, a network may pair an REG configuring each CCE one by one andmay perform interleaving. For example, REG {0, 6}, {1, 7}, {2, 8}, {3,9}, {4, 10}, and {5, 11} may be used in units of interleaving.

<Wideband Reference Signal>

To enhance system flexibility in NR, a method of reducing a common RSand an operation in terms of a UE-specific demodulation reference signal(DMRS) has been discussed. However, a wideband RS may be periodicallytransmitted for the purpose of channel estimation performance andmeasurement of a control channel, phase tracking, and so on. When thewideband RS is used, the number of RSs to be used by a UE during channelestimation may be increased to enhance channel estimation performance.In addition, the UE may perform wideband RS cell or beam levelmeasurement to more effectively perform a procedure such as a cellchange and a beam change.

A UE-dedicated beamforming method, a transmission diversity method, orthe like may be applied to a control channel of NR to transmit controlinformation and, a wideband RS may be more appropriate for thetransmission diversity method. In the UE-dedicated beamforming method,precoding for maximizing a reception SNR depending on a channelsituation of each UE may be applied and, thus, may be more appropriatefor a narrowband operation. Accordingly, use of the transmissiondiversity method may be more appropriate in a resource region in whichthe wideband RS is applied.

In NR, a scheme such as 2-Port space frequency block coding (SFBC),1-Port RB level precoder cycling, and 1-Port stacked cyclic delaydiversity (SCDD) may be used as the transmission diversity method. The1-port RB level precoder cycling may have excellent performance at ahigh AL and may disadvantageously enable decoding using the sameoperation as UE-dedicated beamforming in terms of a UE. However, toapply the wideband RS to the 1-port RB level precoder cycling scheme,additional signaling may be required.

A UE may assume that the same precoder is used in a region in which thewideband RS is transmitted and, thus, may perform channel estimationusing all RSs in the corresponding region and may perform measurement,tracking, or the like. On the other hand, 1-port RB level precodercycling may be a method for acquisition of beam diversity gain usingdifferent precoders for RBs. Accordingly, to simultaneously apply theprecoder cycling scheme and the wideband RS, the following informationelements need to be signaled. The following information elements may beindicated via higher layer signaling or the like or may be signaled inan initial access procedure. All or some of the following informationelements may be signaled to a UE and, when only some of the followinginformation elements, non-signaled information elements may bepredefined.

(i) Period of Wideband RS

A period with which a wideband RS is transmitted, a subframe set, or thelike may be indicated to the UE via higher layer signaling or the like.The UE may perform control channel decoding based on the wideband RS ina slot in which the wideband RS is transmitted.

(ii) Transmission Region of Wideband RS

The time/the frequency domain in a slot in the wideband RS istransmitted may be signaled. The frequency domain of the wideband RS maybe signaled in units of multiples of a UE minimum bandwidth (i.e., aminimum BW specified in NR) and a starting point or the like of thewideband RS may be additionally signaled. A symbol (or symbol set) inwhich the wideband RS is transmitted may also be signaled as the timedomain of the wideband RS.

As another method, a transmission region of the wideband RS may besignaled in units of CORESETs (or subCORESETs). For example, thetransmission region of the wideband RS may be signaled using a method ofadding whether the wideband RS is transmitted or the like to a CORESETconfiguration. For example, as shown in (b) of FIG. 7, when a subCORESETis configured and a wideband RS is applied only to subCORESET0, adifferent precoder from a precoder of subCORESET0 in which the widebandRS is transmitted may be applied to an REG (or REG bundle) ofsubCORESET1.

(iii) The Same Precoding Pattern in Wideband

As described above, when the 1-port RB level precoder cycling is used, aprecoder may be changed for each RB or RB group. Accordingly, an eNB maysignal an RB pattern or the like to which the same precoder is appliedamong regions in which the wideband RS is transmitted. For example, anetwork may notify a UE about precoding information in a resource regionin which the wideband RS is applied.

Although FIG. 9 below exemplifies a method of transmitting precodinginformation to a UE using a concept of a pattern, a sub-pattern, or thelike, the present invention is not limited thereto and precodinginformation may be transmitted using various methods. To reducesignaling overhead or the like, at least some of the following precodinginformation items may be predefined. For example, a precoding relatedpattern in a resource region in which the wideband RS is used may bepredefined. For example, the precoding related pattern may be definedusing the following proposed pattern and sub-pattern, and so on.

FIG. 9 is a diagram for explanation of a method of indicating the sameprecoding pattern according to an embodiment of the present invention.In FIG. 9, the same numeral may refer to application of the sameprecoding.

When 1-port RB level precoder cycling is used, a network may signal apattern length, a sub-pattern length, and the like to notify a UE aboutsections in which the same precoding is applied. Here, the pattern mayrefer to a precoder cycling period and the sub-pattern may refer toresource sections in which the same precoding is applied.

For example, in (a) of FIG. 9, a network may signal a pattern length of6 and a sub-pattern length of 2 to a UE. The UE may apply the patternand the sub-pattern to a section in which the wideband RS is applied toidentify resources to which the same precoding is applied and mayperform channel estimation, measurement, tracking, and so on based onthe corresponding resource.

(b) of FIG. 9 illustrates another example of application of a widebandRS. As shown in (b) of FIG. 9, when the wideband RS is transmitted, thismay be effective to perform measurement for each section. When REG/REGbundles configuring a CCE or different CCEs configuring a candidate aredistributed in different sub-patterns, a valid bundle size may berelatively increased and, thus, frequency diversity gain may be obtainedand channel estimation performance may also be enhanced.

<Configurable RS Density>

With regard to the RS mapping methods proposed in FIG. 4, (a) Type 1 maybe referred to as a full loaded RS method, (b) Type 2 may be referred toas a front loaded RS method, and the front loaded RS method mayadvantageously ensure a lower coding rate for a control signal than thefull loaded RS method.

In addition, a method of lowering a coding rate in the full loaded RSmethod may be proposed. For example, to lower a coding rate, RS densitymay be adjusted based on channel estimation performance.

FIG. 10 illustrates RS patterns for adjusting RS density according to anembodiment of the present invention. In FIG. 10, an RS pattern (i.e., aposition of an RE in which an RS is transmitted) may be changed. Forexample, an RS may be mapped as shown in FIG. 4.

Referring to FIG. 10, RS density may be differently configured accordingto each RS pattern. Accordingly, the number of data REs for transmissionof control information may also be differently configured according toeach RS pattern. All or some of 3 RS patterns may be defined for an NRcontrol channel.

A network may configure an RS pattern with relatively low density for aUE with an excellent channel environment or a UE (or a UE group),channel estimation performance of which is ensured. For example, an RSpattern to be assumed by a UE in a corresponding CORESET for eachCORESET may be configured. The UE may assume an RS pattern in thecorresponding CORESET according to an RS configuration for each CORESET.

An RS pattern to be assumed by a UE in each CORESET may be determined inassociation with CORESET duration (without additional signaling). Forexample, when configurable CORESET duration is 1, 2, and 3 symbols, a UEmay assume that RS patterns are used in respective durations. WhenCORESET duration is 1, (a) ⅓ RS pattern may be used, when CORESETduration is 2, ¼ RS pattern may be used, and when CORESET duration is 3,use of ⅙ RS pattern may be configured/predefined.

Application of such association between CORESET duration and an RSpattern may be determined according to whether time domain bundling isperformed. For example, in the case of a CORESET to which time domainbundling (e.g., a UE may assume that the same precoding is applied toREGs belonging to the same bundle in the time domain) is applied, apredetermined RS pattern may be used according to CORESET duration. Whenthe time domain bundling is not applied, only a specific RS pattern(e.g., ⅓ RS pattern) may be predefined to be used irrespective ofCORESET duration. This is because, when the time domain bundling isapplied, channel estimation performance is enhanced compared with timedomain bundling and, thus, even if RS density per REG is lowered,channel estimation performance is not largely degraded.

Through such a method, additional coding gain may be obtained whilechannel estimation performance is ensured. For example, when an RSpattern with low density is used, a similar effect to Type 2 of FIG. 4may be expected.

An RS pattern to be assumed by a UE in each CORESET may be determined inassociation with a bundling option of each CORESET (without additionalsignaling). REG bundling may be possible with respect to NR-PDCCH in thetime/frequency domain and performance enhancement may be expected viaREG bundling in terms of channel estimation. As such, when sufficientchannel estimation performance is capable of being obtained via REGbundling, it may be desirable to lower RS density to acquire gain interms of a coding rate.

Accordingly, according to an embodiment of the present invention, RSdensity may be determined in association with a whole bundle size. Forexample, in the time/frequency domain, a bundle size may be representedaccording to (Time, Frequency)=(1, 6), (2, 3), (3, 2), (2, 1), (3, 1)(where, in the case of 1 symbol CORESET, (1, 2) and (1, 3) are alsopossible) and, when the sum of bundle sizes of the time and frequencydomains is equal to or greater than 5, an RS pattern corresponding to RSdensity of ⅙ may be used. On the other hand, when the sum of bundlesizes in the time and frequency domains is less than 5, an RS patterncorresponding to RS density of ⅓ may be applied.

As another example, when time domain bundling is used for the purpose ofreducing of a coding rate (e.g., an RS is transmitted only to some ofREGs of the time domain bundle), RS density may be determined based on afrequency domain bundle size. For example, the frequency domain bundlesize is greater than 2 REGs, an RS pattern corresponding to RS densityof ⅙ may be used and, when the frequency domain bundle size is 1 or 2,an RS pattern corresponding to RS density of ⅓ and ¼ may be used.

The above proposed configurable RS pattern (or CORESET duration-based RSpattern) may enhance efficiency in terms of channel estimationperformance and a coding rate but an operating method for the case inwhich CORESETs with different CORESET durations overlap with each otherneeds to be defined.

FIG. 11 illustrates the case in which CORESETs with different CORESETdurations overlap with each other according to an embodiment of thepresent invention.

Referring to FIG. 11, CORESET 0 of Duration 1 and CORESET 1 of Duration3 may partially overlap with each other. It may be assumed that ⅓ RSpattern is used in CORESET0 and time domain bundling is applied and ⅙ RSpattern is used in CORESET1 (e.g., a bundle size: 1 in the frequencydomain & 3 in the time domain). In this case, an RS pattern isredundantly configured in Region0 and, thus, when how an RS patterns isprocessed in Region 0 is not defined, there may be a problem in that aUE wrongly refers to an RS during blind decoding of the UE as well aschannel estimation or decoding performance is degraded.

To overcome a problem that arises when RS patterns are configured tooverlap with each other in the time/frequency domain due to overlapbetween different CORESETs, the following methods (i) to (iv) areproposed. A specific option among the following options may bepredefined to be used when CORESETs overlap with each other or may beconfigured for a UE by a network. In addition, the following options mayalso be applied when CORESETs overlap with each other irrespective of anRS pattern (e.g., even when RS patterns of different CORESETs are thesame).

(i) Option 1: Assumption of Only RS Pattern of Corresponding CORESET

For an NR-PDCCH, a UE-specific DMRS may be basically used. Accordingly,a UE may assume only an RS pattern of a corresponding CORESET whileperforming blind decoding on a control channel candidate that belongs toa specific CORESET. For an operation such as Option 1, it may be assumedthat a network does not transmit different PDCCHs to the same resourceusing the same RS portion. For example, it may be assumed that an RSpattern configured in CORESET1 is always used in Regions 1 and 2 in FIG.11. The UE may assume that only an RS pattern of CORESET0 is presentwhile performing blind decoding on a candidate of CORESET0 in Region 0,may assume that only an RS pattern of CORESET1 while performing blinddecoding on a candidate of CORESET1 in Region 0, and may perform blinddecoding.

(ii) Option 2: Change in RS Pattern

When a plurality of CORESETs are configured for one UE and a section inwhich CORESETs overlap with each other in the time/frequency domain ispresent, an RS pattern of a specific CORESET may be changed in allCORESETs or a section in which the CORESETs overlap with each other. Tothis end, a network may configure RS pattern information (e.g., v-shiftinformation indicating frequency shift) of a corresponding CORESETtogether while configuring a CORESET.

Alternatively, a UE may assume that an RS pattern of a specific CORESETis changed to a predefined pattern when CORESETs overlap with each otherwithout signaling of a network.

To this end, priority between CORESETs may be defined and an RS patternof a CORESET with low priority may be changed. A CORESET with highpriority may be, for example, a CORESET in which an RS (e.g., widebandRS) transmitted irrespective of whether a PDCCH is transmitted and a UEmay assume that an RS pattern of such a CORESET is not changed.

When an RS pattern is changed to a predefined pattern, the predefinedpattern may be defined through, for example, a v-shift value (e.g., aposition of an RS is moved by a v-shift value in the frequency domain).

(iii) Option 3: Rate-Matching of Different CORESET

It may be assumed that an RS (e.g., Wideband RS) transmittedirrespective of whether a PDCCH is transmitted is transmitted in aspecific CORESET (or specific time/the frequency domain) and thatanother CORESET that overleaps with the corresponding CORESET isconfigured. In this case, a UE may assume that RS pattern positions ofdifferent CORESETs are rate-matched in mapping of control informationwhile performing blind decoding on each CORESET.

In this case, since control information is rate-matched with respect toan RS pattern position, a coding rate of the control information may beincreased and, as a result, decoding performance of the UE may bedegraded. When RS patterns are redundantly configured in the sametime/frequency resource, an RS may not be frequently used in acorresponding region. For example, when ⅓ RS pattern and ⅙ RS pattern ofFIG. 10 are used in different CORESETs, respectively, RS REs accordingto the ⅙ RS pattern may be redundantly configured as RS REs according tothe ⅓ pattern.

To overcome this problem, when Option 3 is used, an RS pattern needs tobe determined in such a way that RS RE positions are not redundantbetween RS patterns. To prevent an RE in which an RS is transmitted frombeing redundant, the method of changing an RS pattern configured inOption 2 may also be used.

(iv) Option 4: Use of RS Pattern of CORESET with High Priority

When an RS (e.g., wideband RS) transmitted irrespective of whether aPDCCH is transmitted in a specific CORESET (or specific time/thefrequency domain) and another CORESET that overlaps with thecorresponding CORESET is configured, a UE may assume only an RS patternof a CORESET with high priority in a section (e.g., region 0 of FIG. 11)in which CORESETs overlap with each other while performing blinddecoding on each CORESET. For example, the UE may assume that an RSpattern defined in a CORESET with low priority is not used in a sectionin which CORESETs overleap with each other.

Priority of CORESETs may be configured by a network or may bepredefined. When the priority of CORESETs is predefined, high prioritymay be assigned to a CORESET including a common search space, a CORESETin which a wideband RS (e.g., RSs that are transmitted at a timeinterval in a predetermined region irrespective of whether a PDCCH istransmitted) is transmitted, or the like.

When a CORESET in which a wideband RS is transmitted and a CORESET inwhich a DMRS is transmitted entirely or partially overlap with eachother (e.g., when a wideband RS is used in CORESET 0 and a DMRS is usedin CORESET1 in FIG. 11) and Option 3 or Option 4 is used, even if timedomain bundling is applied to CORESET1, a UE may separately performchannel estimation with respect to each of Region0 and Region1. Forexample, the UE may apply the channel estimation result using thewideband RS to a corresponding REG in Region0 and may apply the channelestimation result using the DMRS to the corresponding to REG in Region1.In this case, the UE may assume that time domain bundling is appliedonly to Region1. A time domain bundle size in a region in which CORESETsoverlap with each other may be interpreted to be different from a bundlesize of a corresponding CORESET. Time domain bundling may be determinedaccording to a configuration of a CORESET in Region2.

FIG. 12 illustrates a flow of a method of transmitting and receivingdownlink control information (DCI) according to an embodiment of thepresent invention. FIG. 12 illustrates an example of the aforementionedmethods and the present invention is not limited to FIG. 12 and, thus, arepeated description of the above description may not be given here.

Referring to FIG. 12, an eNB may transmit bundling information onresource element groups (REGs) via higher layer signaling (1205). EachREG may correspond to 1 resource block (RB) and 1 orthogonal frequencydivisional multiplexing (OFDM) symbol. The eNB may transmit bundlinginformation via higher layer signaling of a CORESET configuration.

One or more CORESETs may be configured in one UE. For example, an eNBmay transmit one or more or more CORESET configurations to one UE toconfigure one or more CORESETs. Bundling information and a controlchannel element (CCE)-to-REG mapping type may be indicated (e.g.,indicated though a CORESET configuration) for each CORESET. The bundlinginformation may include bundle size information indicating the number ofREGs included in 1 REG bundle. The CCE-to-REG mapping type of a CORESETmay indicate one of a localized mapping type (e.g., non-interleavedmapping) and an interleaved mapping type.

Hereinafter, for convenience of description, a CCE-to-REG mapping typeof a CORESET is assumed to be configured as an interleaving mappingtype. In addition, a CORESET may be assumed to be configured on aplurality of OFDM symbols. For example, the number of a plurality ofOFDM symbols for configuring a CORESET may be 2 or 3.

The eNB may generate DL control information (DCI) (1210).

The eNB may transmit the generated DCI through a PDCCH (1215).

When bundling information indicates a first value, the eNB may performbundling such that only REGs locating on a same RB and corresponding todifferent OFDM symbols in the CORESET, are bundled as 1 REG bundle. Whenthe bundling information indicates a second value, the eNB may performbundling such that the REGs locating on the same RB and corresponding tothe different OFDM symbols are bundled as 1 REG bundle along with REGslocating on different RBs in the CORESET. The eNB may transmit the DCIby applying same precoding for REGs belonging to a same REG bundle as aresult of REG bundling.

The UE may perform blind detection for a physical downlink controlchannel (PDCCH) in a control resource set (CORESET) configured on aplurality of OFDM symbols (1220).

The UE may acquire DL control information (DCI) from the blind-detectedPDCCH (1225). When the bundling information indicates a first value, theUE may perform bundling such that only REGs locating on a same RB andcorresponding to different OFDM symbols in the CORESET, are bundled as 1REG bundle. When the bundling information indicates a second value, theUE may perform bundling such that the REGs locating on the same RB andcorresponding to the different OFDM symbols are bundled as 1 REG bundlealong with REGs locating on different RBs in the CORESET. For example,when the bundling information indicates the first value, the UE mayperform time domain REG bundling and, when the bundling informationindicates the second value, the UE may perform time-frequency domain REGbundling.

The UE may perform the blind detection for the PDCCH by assuming sameprecoding for REGs which belong to a same REG bundle as a result of REGbundling. For example, the UE may perform demodulation for the PDCCH byassuming that the same precoding is applied to RSs received through REGsbelonging to the same REG bundle and.

When the bundling information indicates the first value, 1 REG bundlesize may be configured to be the same as the number of the plurality ofOFDM symbols for configuring a CORESET.

When the bundling information indicates the second value, 1 REG bundlesize may be configured to be the same as the number of REGs included in1 control channel element (CCE).

Interleaving for CCE-to-REG mapping may be performed in a unit of a REGbundle using an REG bundle index.

A supported bundle size may be determined according to a CCE-to-REGmapping type.

For example, bundling information may include at least one of intra-CCEbundle size information for bundling of REGs belonging to the samecontrol channel element (CCE) and inter-CCE bundle size information forbundling of REGs belonging to different control channel elements (CCEs).When the bundling information includes the inter-CCE bundle sizeinformation, the UE may perform blind detection for the PDCCH byassuming the same precoding with respect to REGs of different CCEsbelonging to the same inter-CCE bundle.

FIG. 13 is a block diagram illustrating a structure of a base station(BS) 105 and a UE 110 in a wireless communication system 100 accordingto an embodiment of the present invention. The structure of the BS 105and the UE 110 of FIG. 13 are merely an embodiment of a BS and a UE forimplementing the aforementioned method and the structure of a BS and aUE according to the present invention is not limited to FIG. 13. The BS105 may also be referred to as an eNB or a gNB. The UE 110 may also bereferred to as a user terminal.

Although one BS 105 and one UE 110 are illustrated for simplifying thewireless communication system 100, the wireless communication system 100may include one or more BSs and/or one or more UEs.

The BS 105 may include a transmission (Tx) data processor 115, a symbolmodulator 120, a transmitter 125, a transmission/reception antenna 130,a processor 180, a memory 185, a receiver 190, a symbol demodulator 195,and a reception (Rx) data processor 197. The UE 110 may include a Txdata processor 165, a symbol modulator 170, a transmitter 175, atransmission/reception antenna 135, a processor 155, a memory 160, areceiver 140, a symbol demodulator 155, and an Rx data processor 150. InFIG. 12, although one antenna 130 is used for the BS 105 and one antenna135 is used for the UE 110, each of the BS 105 and the UE 110 may alsoinclude a plurality of antennas as necessary. Therefore, the BS 105 andthe UE 110 according to the present invention support a Multiple InputMultiple Output (MIMO) system. The BS 105 according to the presentinvention can support both a Single User-MIMO (SU-MIMO) scheme and aMulti User-MIMO (MU-MIMO) scheme.

In downlink, the Tx data processor 115 receives traffic data, formatsthe received traffic data, codes the formatted traffic data, interleavesthe coded traffic data, and modulates the interleaved data (or performssymbol mapping upon the interleaved data), such that it providesmodulation symbols (i.e., data symbols). The symbol modulator 120receives and processes the data symbols and pilot symbols, such that itprovides a stream of symbols.

The symbol modulator 120 multiplexes data and pilot symbols, andtransmits the multiplexed data and pilot symbols to the transmitter 125.In this case, each transmission (Tx) symbol may be a data symbol, apilot symbol, or a value of a zero signal (null signal). In each symbolperiod, pilot symbols may be successively transmitted during each symbolperiod. The pilot symbols may be an FDM symbol, an OFDM symbol, a TimeDivision Multiplexing (TDM) symbol, or a Code Division Multiplexing(CDM) symbol.

The transmitter 125 receives a stream of symbols, converts the receivedsymbols into one or more analog signals, and additionally adjusts theone or more analog signals (e.g., amplification, filtering, andfrequency upconversion of the analog signals), such that it generates adownlink signal appropriate for data transmission through an RF channel.Subsequently, the downlink signal is transmitted to the UE through theantenna 130.

Configuration of the UE 110 will hereinafter be described in detail. Theantenna 135 of the UE 110 receives a DL signal from the BS 105, andtransmits the DL signal to the receiver 140. The receiver 140 performsadjustment (e.g., filtering, amplification, and frequencydownconversion) of the received DL signal, and digitizes the adjustedsignal to obtain samples. The symbol demodulator 145 demodulates thereceived pilot symbols, and provides the demodulated result to theprocessor 155 to perform channel estimation.

The symbol demodulator 145 receives a frequency response estimationvalue for downlink from the processor 155, demodulates the received datasymbols, obtains data symbol estimation values (indicating estimationvalues of the transmitted data symbols), and provides the data symbolestimation values to the Rx data processor 150. The Rx data processor150 performs demodulation (i.e., symbol-demapping) of data symbolestimation values, deinterleaves the demodulated result, decodes thedeinterleaved result, and recovers the transmitted traffic data.

The processing of the symbol demodulator 145 and the Rx data processor150 is complementary to that of the symbol modulator 120 and the Tx dataprocessor 115 in the BS 205.

The Tx data processor 165 of the UE 110 processes traffic data inuplink, and provides data symbols. The symbol modulator 170 receives andmultiplexes data symbols, and modulates the multiplexed data symbols,such that it can provide a stream of symbols to the transmitter 175. Thetransmitter 175 obtains and processes the stream of symbols to generatean uplink (UL) signal, and the UL signal is transmitted to the BS 105through the antenna 135. The transmitter and the receiver of UE/BS canbe implemented as a single radio frequency (RF) unit.

The BS 105 receives the UL signal from the UE 110 through the antenna130. The receiver processes the received UL signal to obtain samples.Subsequently, the symbol demodulator 195 processes the symbols, andprovides pilot symbols and data symbol estimation values received viauplink. The Rx data processor 197 processes the data symbol estimationvalue, and recovers traffic data received from the UE 110.

A processor 155 or 180 of the UE 110 or the BS 105 commands or indicatesoperations of the UE 110 or the BS 105. For example, the processor 155or 180 of the UE 110 or the BS 105 controls, adjusts, and managesoperations of the UE 210 or the BS 105. Each processor 155 or 180 may beconnected to a memory unit 160 or 185 for storing program code and data.The memory 160 or 185 is connected to the processor 155 or 180, suchthat it can store the operating system, applications, and general files.

The processor 155 or 180 may also be referred to as a controller, amicrocontroller), a microprocessor, a microcomputer, etc. In themeantime, the processor 155 or 180 may be implemented by various means,for example, hardware, firmware, software, or a combination thereof. Ina hardware configuration, methods according to the embodiments of thepresent invention may be implemented by the processor 155 or 180, forexample, one or more application specific integrated circuits (ASICs),digital signal processors (DSPs), digital signal processing devices(DSPDs), programmable logic devices (PLDs), field programmable gatearrays (FPGAs), processors, controllers, microcontrollers,microprocessors, etc.

In a firmware or software configuration, methods according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. which perform the above-describedfunctions or operations. Firmware or software implemented in the presentinvention may be contained in the processor 155 or 180 or the memoryunit 160 or 185, such that it can be driven by the processor 155 or 180.

Radio interface protocol layers among the UE 110, the BS 105, and awireless communication system (i.e., network) can be classified into afirst layer (L1 layer), a second layer (L2 layer) and a third layer (L3layer) on the basis of the lower three layers of the Open SystemInterconnection (OSI) reference model widely known in communicationsystems. A physical layer belonging to the first layer (L1) provides aninformation transfer service through a physical channel. A RadioResource Control (RRC) layer belonging to the third layer (L3) controlsradio resources between the UE and the network. The UE 110 and the BS105 may exchange RRC messages with each other through the wirelesscommunication network and the RRC layer.

The above-mentioned embodiments correspond to combinations of elementsand features of the present invention in prescribed forms. And, it isable to consider that the respective elements or features are selectiveunless they are explicitly mentioned. Each of the elements or featurescan be implemented in a form failing to be combined with other elementsor features. Moreover, it is able to implement an embodiment of thepresent invention by combining elements and/or features together inpart. A sequence of operations explained for each embodiment of thepresent invention can be modified. Some configurations or features ofone embodiment can be included in another embodiment or can besubstituted for corresponding configurations or features of anotherembodiment. And, it is apparently understandable that an embodiment isconfigured by combining claims failing to have relation of explicitcitation in the appended claims together or can be included as newclaims by amendment after filing an application.

While the present invention has been described and illustrated hereinwith reference to the preferred embodiments thereof, it will be apparentto those skilled in the art that various modifications and variationscan be made therein without departing from the spirit and scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention that come within thescope of the appended claims and their equivalents.

As described above, the present invention may be applied to variouswireless communication systems.

What is claimed is:
 1. A method of receiving a physical downlink controlchannel (PDCCH) by a user equipment (UE) in a wireless communicationsystem, the method comprising: receiving bundle size information relatedto a bundle size of resource element groups (REGs) over which sameprecoding is applied, each REG occupying 1 resource block (RB) in afrequency domain during 1 orthogonal frequency divisional multiplexing(OFDM) symbol in a time domain; and receiving the PDCCH consisting of atleast one control channel element (CCE) on a control resource set(CORESET) configured with a plurality of REG bundles in a CORESETduration that spans a plurality of OFDM symbols in the time domain,wherein the plurality of REG bundles in the CORESET are mapped to CCEswith each CCE comprising 6 REGs, and wherein, based on the bundle sizeof REGs by the bundle size information being a first bundle size, onlyREGs that occupy a same RB in the frequency domain and L OFDM symbols inthe time domain are bundled as one REG bundle, where L is equal to anumber of the plurality of OFDM symbols that configure the CORESETduration.
 2. The method of claim 1, wherein, based on the bundle size ofthe REGs by the bundle size information being a second bundle sizedifferent from the first bundle size, REGs that occupy different RBs inthe frequency domain and different OFDM symbols in the time domain arebundled as one REG bundle, where the second bundle size is equal to aninteger multiple of the number of the plurality of OFDM symbols thatconfigure the CORESET duration.
 3. The method of claim 2, wherein thesecond bundle size is equal to
 6. 4. The method of claim 1, wherein aplurality of CORESETs comprising the CORESET are configured for the UE,and wherein the method further comprises: receiving, for each of theplurality of CORESETs, a corresponding bundle size information for REGsin the CORESET.
 5. The method of claim 1, wherein the number of theplurality of OFDM symbols that configure the CORESET duration is equalto 2 or
 3. 6. An apparatus comprising: at least one processor; and atleast one computer memory operably connectable to the at least oneprocessor and storing at least one program that, when executed, causesthe at least one processor to perform operations that comprise:receiving bundle size information related to a bundle size of resourceelement groups (REGs) over which same precoding is applied, each REGoccupying 1 resource block (RB) in a frequency domain during 1orthogonal frequency divisional multiplexing (OFDM) symbol in a timedomain; and receiving a physical downlink control channel (PDCCH)consisting of at least one control channel element (CCE) on a controlresource set (CORESET) configured with a plurality of REG bundles in aCORESET duration that spans a plurality of OFDM symbols in the timedomain, wherein the plurality of REG bundles in the CORESET are mappedto CCEs with each CCE comprising 6 REGs, and wherein, based on thebundle size of REGs by the bundle size information being a first bundlesize, only REGs that occupy a same RB in the frequency domain and L OFDMsymbols in the time domain are bundled as one REG bundle, where L isequal to a number of the plurality of OFDM symbols that configure theCORESET duration.
 7. The apparatus of claim 6, wherein, based on thebundle size of the REGs by the bundle size information being a secondbundle size different from the first bundle size, REGs that occupydifferent RBs in the frequency domain and different OFDM symbols in thetime domain are bundled as one REG bundle, where the second bundle sizeis equal to an integer multiple of the number of the plurality of OFDMsymbols that configure the CORESET duration.
 8. The apparatus of claim7, wherein the second bundle size is equal to
 6. 9. The apparatus ofclaim 6, wherein a plurality of CORESETs comprising the CORESET areconfigured, and wherein the operations further comprise: receiving, foreach of the plurality of CORESETs, a corresponding bundle sizeinformation for REGs in the CORESET.
 10. The apparatus of claim 6,wherein the number of the plurality of OFDM symbols that configure theCORESET duration is equal to 2 or
 3. 11. A computer readable storagemedium storing at least one program that, when executed, causes at leastone processor to perform operations that comprise: receiving bundle sizeinformation related to a bundle size of resource element groups (REGs)over which same precoding is applied, each REG occupying 1 resourceblock (RB) in a frequency domain during 1 orthogonal frequencydivisional multiplexing (OFDM) symbol in a time domain; and receiving aphysical downlink control channel (PDCCH) consisting of at least onecontrol channel element (CCE) on a control resource set (CORESET)configured with a plurality of REG bundles in a CORESET duration thatspans a plurality of OFDM symbols in the time domain, wherein theplurality of REG bundles in the CORESET are mapped to CCEs with each CCEcomprising 6 REGs, and wherein, based on the bundle size of REGs by thebundle size information being a first bundle size, only REGs that occupya same RB in the frequency domain and L OFDM symbols in the time domainare bundled as one REG bundle, where L is equal to a number of theplurality of OFDM symbols that configure the CORESET duration.
 12. Thecomputer readable storage medium of claim 11, wherein, based on thebundle size of the REGs by the bundle size information being a secondbundle size different from the first bundle size, REGs that occupydifferent RBs in the frequency domain and different OFDM symbols in thetime domain are bundled as one REG bundle, where the second bundle sizeis equal to an integer multiple of the number of the plurality of OFDMsymbols that configure the CORESET duration.
 13. The computer readablestorage medium of claim 12, wherein the second bundle size is equal to6.
 14. The computer readable storage medium s of claim 11, wherein aplurality of CORESETs comprising the CORESET are configured for a userequipment (UE), and wherein the operations further comprise: receiving,for each of the plurality of CORESETs, a corresponding bundle sizeinformation for REGs in the CORESET.
 15. The computer readable storagemedium of claim 11, wherein the number of the plurality of OFDM symbolsthat configure the CORESET duration is equal to 2 or
 3. 16. A basestation for transmitting a physical downlink control channel (PDCCH) ina wireless communication system, the base station comprising: at leastone processor; and at least one computer memory operably connectable tothe at least one processor and storing at least one program that, whenexecuted, causes the at least one processor to perform operations thatcomprise: transmitting bundle size information related to a bundle sizeof resource element groups (REGs) over which same precoding is applied,each REG occupying 1 resource block (RB) in a frequency domain during 1orthogonal frequency divisional multiplexing (OFDM) symbol in a timedomain; and transmitting the PDCCH consisting of at least one controlchannel element (CCE) on a control resource set (CORESET) configuredwith a plurality of REG bundles in a CORESET duration that spans aplurality of OFDM symbols in the time domain, wherein the plurality ofREG bundles in the CORESET are mapped to CCEs with each CCE comprising 6REGs, and wherein, based on the bundle size of REGs by the bundle sizeinformation being a first bundle size, only REGs that occupy a same RBin the frequency domain and L OFDM symbols in the time domain arebundled as one REG bundle, where L is equal to a number of the pluralityof OFDM symbols that configure the CORESET duration.
 17. The basestation of claim 16, wherein, based on the bundle size of the REGs bythe bundle size information being a second bundle size different fromthe first bundle size, REGs that occupy different RBs in the frequencydomain and different OFDM symbols in the time domain are bundled as oneREG bundle, where the second bundle size is equal to an integer multipleof the number of the plurality of OFDM symbols that configure theCORESET duration.
 18. The base station of claim 17, wherein the secondbundle size is equal to
 6. 19. The base station of claim 16, wherein aplurality of CORESETs comprising the CORESET are configured, and whereinthe operations further comprise: transmitting, for each of the pluralityof CORESETs, a corresponding bundle size information for REGs in theCORESET.
 20. The base station of claim 16, wherein the number of theplurality of OFDM symbols that configure the CORESET duration is equalto 2 or 3.